柴达木盆地北缘地区中侏罗统大煤沟组页岩油形成地质条件

Geological conditions for shale oil forming of Middle Jurassic Dameigou Formation in the northern margin of Qaidam Basin

为研究柴北缘地区大煤沟组七段(J2d7)页岩油形成条件,通过野外地质剖面调查与岩心观察、地质实验与钻井资料相结合,对J2d7泥页岩发育特征、有机地化特征、岩矿特征、储集性能及含油性等进行了综合分析。结果表明:柴北缘地区大煤沟组J2d7富有机质泥页岩厚度大,横向分布稳定,有机质丰度高,有机质类型较好,具有良好的生油能力;J2d7泥页岩段岩性组合类型多样,泥页岩脆性矿物含量较高,发育多种储油孔隙类型;氯仿沥青"A"与S1等指数较高,表明J2d7泥页岩具有较高的滞留油含量。综合研究后认为,柴北缘地区J2d7泥页岩段具备形成页岩油的地质条件,是该区大煤沟组页岩油气勘探最有利的层段,鱼卡断陷、红山断陷、欧南凹陷和德令哈断陷等地区是页岩油勘探的相对有利区。

Based on field geologic section investigation, core observation, geologic test and drilling data, this paper analyzed the development characteristics, organic geochemical behavior, rock mineral features, reservoir properties and oil-bearing capability of shale of the seventh member of Dameigou Formation （J2d^7） in the northern margin of Q aidam Basin. The result shows that the shale with rich organic matter of J2d^7 is thick vertically and continuous laterally, with high organic abundance and good organic type to generate oil. The lithologic assemblage types of J2d^7 shale are various, the percentage of brittle minerals is high, and it developed many kinds of pores and has high content of occluded oil. Comprehensive study demonstrates that shale of J2d^7 has basic geological conditions to form shale oil, and it is the best favorable target for shale oil exploration. Yuka fault depression, Hongshan fault depression, Ounan sag and Delingha fault depression may be the favorable areas for shale oil exploration.